Scooterotica

was thinking of put an air test on a n engine i`m re-building what sort of pressure do i need to put in ? and how long should i expect for the pressure to hold for ?

No greater that 6lbs/ins2 and see the link below for a bit more info. I'm going to have a go over winter with a home made one from a mountain bike inner tube.

http://www.klemmvintage.com/airleaks.htm

To be honest you don't really need to be even that technical. you will find if you a leak the inner tube will pretty much deflate as soon as you stop pumping. if you don't it will hold the air. We used a bicycle pump and it worked well.
All the engines we have tested have had air leaks some of them pretty big. the best way we found of nailing exactly where they were and wether we had sorted them was to invert the top end into a water but suspended by a bit of rod through the engine mounts. then while one was holding the engine vertical the other would pump and hey presto....

And Lo was the Lambretta submarine invented

Donnie wrote:And Lo was the Lambretta submarine invented

the thought did occur to us but by using a water butt we were able to have the rod resting on the water butt edge. this took all the weight and we drained it so it just went past the base gasket.
I know it sounds extreme but if you already have the engine out it only takes a minute and it's the best way visually to see any leaks.
Takes me back to repairing my old bicycle tubes in the kitchen sink...